species of bark from St. Domingo, which was considered at the time as a model for vegetable analysis. It bears the exact characters of the peculiar method followed by Vauquelin. I should suppose therefore, though nothing is said on the subject, that the experiments were contrived and executed by that eminent chemist.

8. His dissertation on the sulphate of mercury, though imperfect, contains some good observations, and facilitated the knowledge of metallic salts, which was at that time very imperfect; but has been greatly improved since. The same remark applies to his subsequent memoirs on the action of ammonia, on the sulphate, nitrate, and muriate, of mercury. These papers contain some mistaken opinions, though the formation of the triple salts, which constitutes the basis of his opinion, be correct.

9. His experiments on the brain contains several valuable facts, and his opinion approaches to accuracy. The subject has been recently resumed by Vauquelin, who has published a curious dissertation on it, which we shall insert in the present number of the Annals of Philosophy.

10. The analysis of tears, and the mucus of the nose, by Fourcroy and Vauquelin, is valuable; though it contains some mistakes, from the too hasty application of an erroneous theory to the animal phenomena.

11. The analysis of urine, and of urinary calculi, by the same gentleman, has been much admired on the Continent, and no doubt contains many important facts; but hardly any important addition is made in it to the dissertation of Dr. Wollaston on the same subject, which had been already published in the Philosophical Transactions. To this very important paper no allusion whatever is made; yet they could hardly be ignorant of it, as they quote Dr. Pearson's essay on the same subject, which had been published in the same work.

12. Their experiments on the combustion of bodies in oxymuriatic acid gas, and the detonations which take place when hyperoxymuriate of potash and a combustible substance are mixed together and struck upon an anvil, are curious, though they add but little to the improvement of the theory of chemistry.

13. Their method of obtaining barytes in a state of purity, by exposing the nitrate of barytes to a red heat in a porcelain crucible, is a good one; and is by far the easiest way to procure that earth in a state of tolerable purity.

14. Their theory of the formation of sulphuric ether, by the action of sulphuric acid, is plausible; and at least as likely to be true as any other explanation which has been hitherto offered: but they were wrong in attempting to extend that theory to the

formation of ether in general. We now know that the nitric, and muriatic, and acetic ether, are formed in quite a different

manner.

15. They ascertained by experiment that the three liquids, known by the names of pyromucous, pyrolignous, and pyrotartarous acids, are nothing else than vinegar holding in solution a portion of empyreumatic oil.

16. They ascertained the presence of phosphate of magnesia in the bones of all animals.

17. Their experiments upon crude platina were not so successful. They detected in it the presence of a new metal. But as they in fact confounded the two metals of Tennant, the osmium and iridium, together, all their observations were either erroneous, or so confused that it was impossible to disentangle the truth from them.

18. Their experiments on the bitter principle extracted from indigo, and the detonating property which it possesses, are curious. The subject was carried farther by Hatchett and Chevreul.

19. They were unsuccessful in their attempts to detect the presence of fluoric acid in bones; though this was afterwards successfully executed by Berzelius.

20. They discovered a quantity of uncombined phosphorus in the melts of fishes. They showed, likewise, an analogy between the pollen of the antheræ of some flowers, and the seminal fluid of animals.

21. They detected in the common onion the presence of a considerable quantity of saccharine matter, and showed by experiment that this saccharine matter was converted into manna by a spontaneous change which it underwent. They found, at the same time, that manna is incapable of undergoing the vinous fermentation, and, of course, that it does not yield alcohol.

22. They ascertained the properties of animal mucus, and showed that it differed from all other animal substances.

23. These, though only a small number of the chemical papers published by Fourcroy, are by far the most important. We have no means of determining what portion of each belongs to Fourcroy, and what to Vauquelin; but there is one merit, at least, which cannot be refused Fourcroy, and it is no small one. He formed and brought forwards Vauquelin, and proved to him ever afterwards a most steady and indefatigable friend. This is bestowing no small panegyric on his character; for it would have been impossible to have retained such a friend through all the horrors of the French revolution, if his own qualities had not been such as to merit so steady an attachment. I have taken

no notice of the labours of M. de Fourcroy in the chemical part of the Encyclopedie Methodique, though they are rather voluminous, because I conceive them of inferior importance to those which I have noticed.

ARTICLE II.

Analysis of the Cerebral Matter of Man, and some other Animals. By M. Vauquelin.*

SECT. I.

History of the chemical labours hitherto undertaken on the cerebral matter.

Although the brain, in consequence of the functions which it is supposed to perform, ought to have early excited the curiosity of chemists, yet one is surprised to find but very little in their works concerning its chemical nature. Even the small number of experiments which have been undertaken have not been pushed far enough to enable us to deduce any positive consequences. Hence the opinions formed respecting the composition of the brain are erroneous, or at least incomplete. It was therefore necessary to resume the subject from the commencement, and to employ that care and precision which the difficulty of the subject rendered necessary. I have undertaken this difficult task. I submit the results which I have obtained to the chemists. It is their province to judge how far I have succeeded.

Gurman first announced the long period during which the brain remains sound in the cranium of dead bodies.

Burrhus compared this organ to an oil, and particularly to spermaceti.

Thouret, whose loss medicine laments, in an excellent memoir on the dead bodies found in the burying-ground of the Innocents, considered the substance of the brain as a sort of soap.

Fourcroy, whom the sciences likewise deplore, advanced an opinion respecting the nature of the cerebral matter different from that of Thouret. † He considered it as principally composed of albumen and of another matter, which he thought a peculiar substance. Though the experiments of Fourcroy leave several things imperfect, yet it will be seen, by comparing them

From the Annales de Chimie, vol. Ixxxi. p. 37.
Annales de Chimie, yol. xvi,

with mine, that his account of the brain is by far the completest hitherto given, and that it approaches pretty closely to the truth.

SECT. II.

Treatment of the brain with alcohol, or spirit of wine.

A portion of human brain, deprived of its envelopes, and reduced to a homogeneous pulp in a marble mortar by means of a wooden pestle, was mixed with about five times its weight of alcohol of 36 degrees. This mixture, left to macerate during 24 hours, was heated to the boiling temperature, and passed through the filter.

The alcohol had acquired a greenish colour. It deposited, on cooling, a white matter, partly in flocks, and partly in plates. Twelve hours after the cooling, the alcohol was filtered again. It still retained its green colour. Water destroyed its transparency, and rendered it milky.

This alcohol, being evaporated till only one eighth part of it remained, deposited, on cooling, an oily matter, yellowish and fluid, which sunk to the bottom of the vessel. The liquid itself continued yellowish.

We shall hereafter examine this oily matter, together with the liquor which accompanied it.

The alcohol obtained by distillation was poured upon the cerebral matter, already once digested with alcohol, as has been already said.

After having boiled the mixture for a quarter of an hour, the alcohol was filtered while hot. It passed through the filter with a colour approaching to blue, and deposited, on cooling, a white matter, as in the first operation, but less abundant. The alcohol, after having deposited this matter, still became milky when mixed with water. This alcohol, when distilled, passed without colour; and the residue of the distillation, which amounted to about the 28th part of the liquid subjected to distillation, had lost its green colour, and acquired a yellow colour.

This residue exhibited two sorts of liquors; one which had the aspect of an oil, and occupied the bottom of the vessel; the other, less coloured, resembled a solution of gum.

We defer the examination of these two liquids till we come to describe those which were obtained by the first operation, because we suspect them to be of the same nature.

The white matter deposited by alcohol in the first operation, and that which the same liquid allowed to deposite in the second operation, had a pasty consistence, a greasy and glutinous feel, a brilliant and satiny appearance.

The last portion was whiter and more solid; but being melted, it was changed, like the first, upon being brought near the flame of a candle.

These substances, when dried upon filtering paper, rendered it transparent, and stained it as an oil would have done.

The matter, which had been retained in solution by the alcohol, and which had been separated by the distillation of this liquid, had a yellow colour, and was of the consistence of a paste, and adhesive. When dried, it dissolved again in boiling alcohol; but before entering into combination with the liquid, it melted at the bottom of the vessel, and assumed the appearance of an oil. The alcoholic solution deposites, on cooling, two matters, which probably differ from each other in the aspect only the one, which precipitates first, attaches itself to the sides of the vessel under the form of a yellow, thick, tenacious fat; the other remains suspended in the liquor, under the form of scales, white and brilliant like boracic acid..

:

SECT. III.

Desiccation of the Brain.

Nine ounces, one gros (about 292 grammes, or 4312 grains troy, or very nearly three quarters of a troy pound), of cerebral matter, when dried over the water-bath, were reduced to two ounces, or nearly to a fifth part of their original weight; but the desiccation was not complete. These two ounces of matter, burnt in a platinum crucible, decrepitated and melted, and produced a smoke, which had the odour of an empyreumatic oil. This oil, in burning, gave a yellowish white and very large flame, and deposited a great deal of lamp black. Then the odour of the empyreumatic oil became imperceptible. As soon as the flame ceased, the crucible was withdrawn from the fire. The charcoal which it contained weighed 5 grammes (1 gros, 25 grains; or 78.7 grains troy). It was reduced to powder, and exposed again to heat in a platinum crucible. Though exposed to a violent heat, it did not appear to burn; but softened, assuming a pasty form.

After having been exposed for an hour to a white heat, its weight was still 4·68 grammes (724 grains troy); so that it had only lost 38 hundred parts of a gramme, which demonstrates a very difficult combustion in this charcoal.

Being washed with boiling water, and dried, it now weighed only 2.36 grammes (36-5 grains troy). Hence it had lost 2.32 grammes.

The solution strongly reddened the tincture of litmus; and the precipitate which lime-water formed in it was redissolved, till the excess of acid was saturated.